In general, amplifiers are used to increase the power of signals. For example, amplifiers can be used to convert low-power radio frequency (RF) signals into larger RF signals for driving the antenna of a transmitter. In such cases, amplifiers may be implemented as part of an overall power amplifier used by an RF transmission system.
Power amplifiers tend to consume a significant portion of the total power consumed by a transmission system. Therefore, the power amplifier's efficiency (i.e., the power of the amplifier output signal divided by the total power consumed by the amplifier) is an amplifier quality that designers consistently strive to increase.
However, amplifier bandwidth is also an important parameter to consider, and many amplifier designs with high theoretical power efficiencies may have characteristically lower fractional bandwidths, where the fractional bandwidth is the bandwidth of the amplifier divided by the center frequency of the amplifier. Therefore, there remains a need for amplifiers that provide both relatively high efficiency and relatively high fractional bandwidth.